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Guest induced reversible on–off switching of elastic frustration in a 3D spin crossover coordination polymer with room temperature hysteretic behaviour
Chemical Science ( IF 7.6 ) Pub Date : 2020-11-23 , DOI: 10.1039/d0sc04420b
Lucía Piñeiro-López 1 , Francisco-Javier Valverde-Muñoz 1 , Elzbieta Trzop 2 , M Carmen Muñoz 3 , Maksym Seredyuk 1, 4 , Javier Castells-Gil 1 , Iván da Silva 5 , Carlos Martí-Gastaldo 1 , Eric Collet 2 , José Antonio Real 1
Affiliation  

A binary reversible switch between low-temperature multi-step spin crossover (SCO), through the evolution of the population γHS(T) with high-spin (HS)-low-spin (LS) sequence: HS1LS0 (state 1) ↔ HS2/3LS1/3 (state 2) ↔ HS1/2LS1/2 (state 3) ↔ HS1/3LS2/3 (state 4) ↔ HS0LS1 (state 5), and complete one step hysteretic spin transition featuring 20 K wide thermal hysteresis centred at 290 K occurs in the three-dimensional (3D) Hofmann-type porous coordination polymer {FeII(3,8phen)[Au(CN)2]2xPhNO2 (3,8phen = 3,8-phenanthroline, PhNO2 = nitrobenzene), made up of two identical interpenetrated pcu-type frameworks. The included PhNO2 guest (x = 1, 1·PhNO2) acts as a molecular wedge between the interpenetrated 3D frameworks via PhNO2-3,8phen intermolecular recognition and is the source of the strong elastic frustration responsible for the multi-step regime. Detailed X-ray single crystal analysis reflects competition between spatial periodicities of structurally inequivalent HS and LS SCO centres featuring: (i) symmetry breaking (state 3) with ⋯HS–LS⋯ ordering with γHS = 1/2; and (ii) occurrence of spatial modulation of the structure providing evidence for stabilization of local or aperiodic ordered mixed spin states for states 2 and 4 (with γHS ≈ 2/3) and 4 (with γHS ≈ 1/3), respectively. Below c.a. 20 K, structural and magnetic analyses show the photogeneration of a metastable HS*, state 6. The room-temperature single-step hysteretic regime appears with release of the guest (x = 0, 1) and the elastic frustration, and reversibly switches back to the original four-step behaviour upon guest re-adsorption. Both uncommon relevant SCO events meeting in the same material represent a rare opportunity to compare them in the frame of antiferro- and ferro-elastic transitions.

中文翻译:

客体诱导具有室温滞后行为的 3D 自旋交叉配位聚合物中弹性挫折的可逆开关切换

低温多步自旋交叉 (SCO) 之间的二元可逆切换,通过具有高自旋 (HS)-低自旋 (LS) 序列的种群γ HS ( T ) 的演化:HS 1 LS 0 (状态1) ↔ HS 2/3 LS 1/3(状态 2)↔ HS 1/2 LS 1/2(状态 3)↔ HS 1/3 LS 2/3(状态4)↔ HS 0 LS 1(状态5) , 并在三维 (3D) 霍夫曼型多孔配位聚合物 {Fe II (3,8phen)[Au(CN)2 ] 2 x PhNO 2(3,8phen = 3,8-菲咯啉,PhNO 2 = 硝基苯),由两个相同的互穿 pcu 型骨架组成。所包含的 PhNO 2客体 ( x = 1, 1·PhNO 2 )通过PhNO 2 -3,8phen 分子间识别充当相互渗透的 3D 框架之间的分子楔,并且是导致多步骤方案的强弹性挫折的来源. 详细的 X 射线单晶分析反映了结构不等价的 HS 和 LS SCO 中心的空间周期性之间的竞争,其特点是:(i) 对称破坏(状态 3)与⋯HS–LS⋯排序γHS = 1/2 (ii) 结构空间调制的发生为状态 2 和 4(γ HS ≈ 2/3)和 4(γ HS ≈ 1/3)的局部或非周期性有序混合自旋态的稳定提供了证据,分别. 在ca 20 K以下,结构和磁性分析显示亚稳态 HS*,状态 6 的光生。室温单步滞后状态随着客体的释放而出现 ( x = 0, 1) 和弹性挫折,并在客人重新吸附时可逆地切换回原来的四步行为。在相同材料中相遇的两个不常见的相关 SCO 事件代表了在反铁和铁弹性转变的框架中比较它们的难得机会。
更新日期:2020-11-27
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